1. Field of the Invention
The present invention relates to a method of and an apparatus for treating of textile substrates with super critical fluid.
2. Description of the Prior Art
Usually, textile substrates such as, e.g., fibers, yarns, fiber heaps, textile fabrics, or wovens, during their finishing, are repeatedly treated in an aqueous system, e.g. are decoted, bleached, colored, washed and the like.
In meantime, in laboratories, processes were developed in which textile substrates are treated with supercritical fluids, in particular, with supercritical carbon dioxide, for different processing purposes. These processes are described in German Publications Nos. 3,904,515, 4,004,111; 3,904,513; 3,906,724; 3,906,737; 3,906,735; 4,200,352; and 4,344,021. These laboratory-developed processes of treating in supercritical fluids require pressures which vary within a range from 30 bar to 600 bar.
With these laboratory processes, textile substrates, as a rule, tissue samples of an order of several square centimeters, are placed in corresponding laboratory autoclaves and are wetted there with a respective supercritical fluid. However, these processes cannot be transferred to all commercial treating processes.
In the commercial treating processes, a textile substrate is converted into a form suitable for an efficient material flow in a textile finishing operation. Yarns are processed in a form of spools of yarn, webs of textile fabric are processed in a form of rolls.
When the finishing step of wound goods includes treating in a supercritical fluid, the goods in a form of spools or rolls are placed in preliminary cleaned autoclaves. Then, the autoclaves are hermetically sealed, filled with a supercritical fluid and are subjected to a suitable treatment pressure between 30 and 400 bar. The supercritical fluid infiltrate the wound goods. Thereby, the most possible uniform treatment results are achieved, i.e., for all parts of the wound goods, e.g., a uniform color intensity in obtained.
However, in comparison with conventional, diffusion-controlled, receding mass transfer processes, a comparatively longer process duration is observed. This longer process durations is a disadvantage in a commercial textile finishing process. Different suggestions for eliminating this disadvantage became known.
German Publication No. 4,206,952 suggests to reciprocate a piston in the autoclaves so that as a result of this movement, the supercritical fluid flows over and/or through the lapped goods. Therefore, the autoclaves should be equipped with pressure vessels with a volume larger than necessary for receiving only the textile goods, as an additional volume for accommodating the piston movement should be provided. This presents a drawback.
German Publication No. 4,206,954 suggests to equip an autoclave with a circulation pump and to subject the wound goods to the over-flow and/or through-flow of the circulating supercritical fluid. In order to achieve uniform results of the treatment, the autoclave is divided in several parallel or separate region subjected to the action of a supercritical fluid. Each region receives a portion of the wound goods. In order to achieve uniform treatment results for all of the portions, each portion is subjected to a complete circulation flow and, finally all portions are simultaneously subjected, side by side, to a portion of a circulating flow.
A drawback is a complex construction of the apparatus and an additional duration of the process associated with treatment of the product with fluid during parallel discharge, which is necessary to achieve uniformity.
German Publication No. 4,206,955 discloses an apparatus for processing in supercritical fluids and an autoclave of which for receiving the textile substrate is associated with at least two pumps. The supercritical fluid is circulated through the autoclave with one pump, with the other pump serving for delivery of a treatment gas which is in a subcritical condition. One pump is designed for a high delivery output to provide for uniform treatment results in textile substrates. Driving two different pumps performing substantially the same task, with the two pumps operating simultaneously only for a short time, is economically not an optimal solution.
German publication No. 4,206,956 discloses an apparatus for treating textile substrates and including at least two autoclaves. The autoclave can be connected with each other to provide for pumping over the treating fluid from one autoclave into another autoclave claded with the treated substrate for the purpose of substrate tapping. Also, circulation of a supercritical fluid through one or several, arranged in a row, autoclaves is contemplated. A drawback consists in that in order to meet to the requirements of a commercial operation of textile finishing, a number of autoclaves and an associated complex conduit system is needed.
In order to create conditions,which are better than existing conditions, for the commercial use of the processes described in the introduction, and particularly those described in publications Nos. 3,904,515; 4,004,111; 3,904,513; 3,906,724; 3,906,737; 3,906,735 and 4,200,352 and which belong to the content of this application, the present invention contemplates the treatment of the textile substrate, with the supercritical fluid at treatment temperatures the values of which are set by a function of the treatment duration.